Assessing the recovery of fish habitat in a Great Lakes Area of Concern using spatial and temporal benchmarks

Background/Question/Methods

Under the Great Lakes Water Quality Agreement of 1987, 43 areas in the Great Lakes were designated Area of Concerns (AOCs). Areas were listed due to impaired ecosystem function ranging from eutrophication to loss of fish habitat and populations. After decades of work, we have made strides to improve the environmental conditions of AOCs through point-source phosphorus control and other remediation actions. As we delist these areas, we require quantitative tools with which to assess whether management actions have improved fish habitats. We use the metric weighted suitable area (WSA), which takes into account the quality and quantity of habitat, and is based on physical habitat characteristics and fish-habitat preferences. In this study, we used WSA in a multiple benchmark approach to assess the recovery of fish habitat in the Bay of Quinte AOC, Lake Ontario. Historically, the Bay of Quinte was a highly productive ecosystem and important to Lake Ontario fisheries. The bay was negatively impacted by pollution and development; remedial actions have been in place since the late 1970s. We evaluated WSA changes in the Bay of Quinte over time and in comparision to other areas in Lake Ontario and the lower Great Lakes.

Results/Conclusions

We found that fish habitat (WSA) in the Bay of Quinte has improved across three important time stanzas (pre-phosphorus management, post-phosphorus management, and post-dreissenid invasion). The improvements in fish habitat were largely related to improvements in water clarity and the expansion of submerged aquatic vegetation beds. Additionally, we found that WSA in the Bay of Quinte ranks highly compared to other coastal areas in Lake Ontario. Likewise, while differences across life stages exist, Quinte provides a similar amount of habitat to Long Point Bay, Lake Erie, an important reference area in the lower Great Lakes. Overall, the assessment shows that fish habitat has improved in the Bay of Quinte over time and that the region remains important habitat within the lower Great Lakes. Such information provides us with a quantitative basis to inform delisting and further restoration action, especially in light of cumulative and future stressors such as climate change.